Density Matrix Doubt: Can Coherance Be Zero?

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SUMMARY

In a density matrix, it is established that some coherences (off-diagonal terms) can indeed be zero while the diagonal terms (populations) remain non-zero. This occurs particularly in equilibrium states where all coherences are zero. The relationship is defined by the equation rhoij=Ci*Cj', indicating that coherences can vanish independently of the populations. Understanding the distinction between "pure states" and "mixed states" is crucial for grasping these concepts.

PREREQUISITES
  • Density matrix formalism
  • Quantum mechanics fundamentals
  • Concept of pure states
  • Concept of mixed states
NEXT STEPS
  • Research the properties of density matrices in quantum mechanics
  • Study the implications of pure states versus mixed states
  • Explore the concept of equilibrium in quantum systems
  • Learn about the role of coherences in quantum information theory
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Quantum physicists, students of quantum mechanics, and researchers in quantum information science will benefit from this discussion.

harish.ravi
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In a density matrix, can some coherances (off diagonal terms) be zero while the diagonal terms(populations) aren't? I am confused because rhoij=Ci*Cj'. How can coherance be zero if Ci and Cj aren't?
 
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Yse, coherences can be zero. If you're at equilibrium, they're all zero.
 
Your density matrix applies to a "pure state" only. Look up "pure states" and "mixed states".
 

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